1. Field of the Invention
The present invention relates to an image reading apparatus.
2. Description of the Related Art
There is known a conventional image reading apparatus which conveys an image sensor at an area located below an original so as to read the original. For example, there is known an image recording apparatus which generates a transfer timing signal at a predetermined time interval while conveying the image sensor (see Japanese Patent Application Laid-open No. 2009-246636). The transfer timing signal is a signal for transferring an image signal generated by the image sensor. The image sensor executes a reading operation every time the transfer timing signal is inputted to the image sensor.
It may happen in this image reading apparatus that the transfer timing signal is generated at a deviated position from an appropriate original-reading position (timing) at which the original is to be read, depending on the velocity of the image sensor. Thus, the transfer timing signal is corrected based on the count number of pulse edge of an encoder signal which is generated and outputted in accordance with a rotation of a motor which conveys the image sensor. Specifically, an error between a target control value and the count number indicating the position of the image sensor is detected each time interval corresponding to the generation cycle (generation period) of the transfer timing signal, and in a case that the error exceeds an allowable range, the transfer timing signal is generated at a shifted timing.